Estimation of heat flow and geothermal gradient from numerical modelling in central Portugal

Abstract

Numerical modelling of heat flow and geothermal gradient is a useful tool in the absence of accurate measurements of such parameters when thermal conductivity and radiogenic heat production are known. This work describes a 2D thermal model that simulates the crust thermal state in Central Portugal aiming geothermal applications and more specifically EGS projects. This study focuses on granitic rocks, namely HHP granites, where estimated surface heat flows reach values in the range of 114 to 130 mW/m2. In addition, the surface heat flow on a metasedimentary cover with various thicknesses was modelled to check its behaviour as a thermal blanket. The surface heat flow values are on the interval 100 to 115 mW/m2. Both surface heat flow values for granites and metasediments are higher than mean published data. The depth for a possible EGS reservoir is predicted to be around 4 to 4.5 km in depth, where the temperature is estimated to reach 150 ºC.